What is the disadvantage of setting up a site-to-site VPN in a clustered-units environment? 

Answer options:

A. VPN connections can be re-established only if the failed master unit recovers.
B. Smart License is required to maintain VPN connections simultaneously across all cluster units.
C. VPN connections must be re-established when a new master unit is elected.
D. Only established VPN connections are maintained when a new master unit is elected.

C

Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/fxos/clustering/ftd-cluster-solution.html#concept_g32_yml_y2b